Security paper or board product and security package

ABSTRACT

A security paper or board product carrying micro or nano structures such as diffractive optical elements is formed in which the diffractive structures are integrated into the security paper or board product in the manufacturing process. A security package carrying diffractive structures is manufactured wherein diffractive structures are integrated into the security package at a manufacturing stage of the security package material. A security package contains authentication information in the form of diffractive structures. The diffractive structures are included in the security package in at least in one of the following forms: as embossed in the package material, as part of the size or paste or resin used in the manufacturing process of the security package, or as part of the ink used in printing the security package or the security package material.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national stage application of InternationalApplication No. PCT/FI01/00540, filed Jun. 7, 2001, and claims priorityon Finnish Application No. 20001367 filed Jun. 8, 2000, the disclosuresof both of which applications are incorporated by reference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to a method for producing a security paperor board product or a security package carrying micro or nano structuressuch as diffractive optical elements for providing information forauthentication. The present invention also relates to a security packagecontaining authentication information in a form of diffractivestructures.

Diffractive optical elements are optical components, which containstructures with dimensions of the order of wavelength of light. Withdiffractive optical elements it is possible to control propagation oflight by macroscopically smooth surfaces containing micro or nanostructures. These structures are later referred to as diffractivestructures. A simple example of a diffractive optical component is aone-dimensional diffraction grating consisting of periodic grooves ofthe order of wavelength. When a white light beam is passed through orreflected from a diffraction grating it is dispersed in a spectrum.“Diffractive Optics for Industrial and Commercial Applications” (editedby Turunen and Wyrowski, Akademie Verlag 1997, ISBN 3-05-501733-1)discloses diffractive optics and components and their use and design.This source is later referred to as “Diffractive Optics”.

It is known from prior art to use diffractive structures as well asother optical security elements as watermarks in valuable documents andproducts for authentication purpose. Diffractive optical securityelements are typically embossed on thin foils and applied on articles tobe marked as separate adhesives. Optical security objects can includevarious elements observable by various methods. According to“Diffractive Optics” these observation methods can be divided intofirst-line, second-line, and third-line inspection levels. First-lineinspection is based on the human senses only, for instance vision,hearing and the tactile senses. Members of the general public, who mustbe able to distinguish counterfeits and forgeries, mainly use first-lineinspection that can be performed by the naked eye. In second-lineinspection, simple tools are used to reveal hidden security objects.Examples of these tools are magnifiers, barcode scanners, laserpointers, ultraviolet sources and automatic teller machines. Third-lineinspection involves forensic investigation of the security elementperformed by experts using advanced techniques and equipment. This kindof equipment is very expensive and is available only in a few researchinstitutes in the world.

Manufacturing of diffractive structures requires advanced and complexsystems, which only are available in advanced laboratories. Thereforediffractive structures are very difficult to forge.

According to “Diffractive Optics”, advantages for using diffractivestructures as security elements are firstly, that they can not bereproduced with colour copiers or modern desktop publishing equipment.Secondly, production of diffractive structures is quite involved and itrequires special equipment and knowledge. Thirdly, the opticallyvariable effects are generally quite noticeable and therefore theyadequately facilitate first line inspection.

Diffractive structures are usually manufactured by microlithographicmethods. U.S. Pat. No. 4,662,653 discloses an optically diffractingsecurity element comprising a continuous reflecting surface, adielectric layer formed contiguous with the reflecting surface, and aplurality of non-continuous reflecting surface portions embedded in thedielectric layer in a predetermined arrangement for storingauthentication information and a process for forming such element.

U.S. Pat. No. 5,862,750 discloses a method for impressionmicroengravings, which reproduce holograms, kinetic holograms ordiffraction patterns, directly on paper through an embossing process. Inthis method paper is subjected to a pre-treatment step prior toembossing said microengravings to paper. The required pre-treatment is ahumidification step, which gives to a paper a degree of humidity between60% and 80% of relative humidity. The humidified paper is then passedthrough an embossing group at a certain temperature and pressure.According to said publication it is not possible to impressmicroengravings directly on untreated paper.

U.S. Pat. No. 5,871,615 discloses security paper carrying a surfaceprofile pattern imparted to the paper during its manufacture whichrequires de-watering of the paper when imparting the profile pattern anddrying thereafter. The tactile surface profile pattern is visible whenviewed under low angle light, which facilitates verification orauthentication of security documents made using the patterned paper.

U.S. Pat. No. 5,981,040 discloses a holographic image produced ofresinous ink comprising metallic particles. This special ink is used forprinting to a sensitive document to form a reflective coating, which isembossed by a shim. The embossed area of the reflective coating reflectslight in a slightly different direction than the remainder of thereflective coating, thereby creating a holographic image.

U.S. Pat. No. 5,974,150 discloses an authentication system comprising amedium having a plurality of elements, which are distinctive, detectableand disposed in an irregular pattern or having an intrinsicirregularity. The system provides authentication of an object byproviding at least two levels of security, which are a physical level,provided by an observable feature an authentication certificate, and aninformation level, provided by encoding a unique characteristic of theauthentication certificate (such as the observable feature) and/orobject to be authenticated in a marking on the certificate.

U.S. Pat. No. 5,961,152 discloses security paper which has a filamentbonded and embedded into paper which has been previously manufactured.The filament is bonded to the paper by an adhesive, or by heat andpressure. The filament may include a combination of security features,such as reflective filaments, fluorescent filaments, and high tensilestrength filaments.

The problems with the prior art security objects are that they areexpensive to manufacture, difficult or expensive to integrate on paperand easy to counterfeit if they are applicable as separate adhesivelabels. The same applies to laminated package materials containingdiffractive foil layers.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a security packagematerial and package that is inexpensive and fast to manufacture inquantity.

A further object of the present invention is to provide a method forembossing security elements directly into security package material.

A further object of the present invention is to provide a method formanufacturing security package material using existing machineryequipped with means for integrating diffractive structures into packagematerial.

A further object of the present invention is to provide a method forprinting security markings directly on the packaging material by usingink, dye, or other suitable colored or colorless painting liquidscontaining diffractive structures.

A further object of the present invention is to provide a manufacturingmethod for a packaging material containing diffractive structures byusing size or paste containing diffractive structures in themanufacturing process of paper or board.

A further object of the present invention is to provide a manufacturingmethod for a packaging material containing diffractive structures byusing furnish containing diffractive structures in the manufacturingprocess of paper or board.

In view of achieving of the objectives stated above and those that willcome out later the method for producing a security paper or boardproduct carrying micro or nano structures is mainly characterised inthat the diffractive structures comprise at least a section that isdetectable only by inspection tools and the diffractive structures areintegrated into the security paper or board product at the manufacturingprocess of said product.

A method for producing a security package carrying micro or nanostructures such as diffractive optical elements is characterised in thatthe diffractive structures comprise at least a section that isdetectable only by inspection tools and the diffractive structures areintegrated into the security package at a manufacturing stage of thesecurity package material.

Security package containing authentication information in a form ofdiffractive structures is characterised in that the diffractivestructures comprise at least a section that is detectable only byinspection tools and the diffractive structures are included in thesecurity package at least in one of the following forms: as embossed inthe package material, as part of the size or paste or resin used in themanufacturing process of the security package, or as part of the inkused in printing the security package or the security package material.

In prior art it is known to transfer diffractive structures to paperwhen remoisturing the paper first. According to the tests by theapplicant it has been found out that it is possible to emboss adiffractive structure directly on paper without any additional preparingstages which would require expensive stages to the paper making process.This embossing process can be integrated to several different parts ofpapermaking, finishing, converting, or printing process.

According to the invention diffractive structures used as securityelements are included in the package itself by inserting the elements tothe package material in the manufacturing stage. No further stages foradding security information is needed. The security elements can beembossed onto the surface of the package material or they can beintegrated as small pieces in paste, size, resin, or furnish of thepaper or board or package material. Diffractive security elements canalso be mixed into the ink, dye, or painting liquids used in printingthe package.

The advantage of the present invention is the possibility to manufacturesecurity packages with low cost and with high security level. This wayforging the package is very difficult and various types of securitymarks and security levels are easily available. The security informationcan be included in any part of the package and it can be in visible formor in hidden form. It is possible to include a very large amount ofinformation in a package when the method of the invention is applied.

Because of the relatively low cost of producing the security packagesaccording to the invention, the present invention can be utilized in thepackage industry manufacturing packages for consumer products liable toforgery, e.g. music CD's, computer products, medicines, cigarettes, orgenerally any brand products.

In a preferred embodiment of the invention a package bearing diffractivestructures with all security inspection levels is produced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in detail withreference to the figures in the accompanying drawing, the inventionbeing however by no means strictly confined to the details of saidembodiments or variations.

FIG. 1 shows an example of diffractive security structures.

FIG. 2 is a side view of a paper machine.

FIG. 3 is a schematic illustration of a calender nip for a papermachine.

FIG. 4 is a schematic illustration of a Condebelt drying system of apaper machine.

FIG. 5 is a schematic illustration of a surface-sizing/pigmenting unit.

FIG. 6 is a schematic illustration of an extrusion coating line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In embossing security elements to the package material in thepapermaking process, an embossing surface containing a plurality ofdiffractive structure shims is needed. A diffractive structure shim is ameans for embossing the diffractive structures to the desired material,such as paper or board or a package material web. The diffractivestructure shims are preferably arranged in a suitably distributed matrixin the embossing surface, which is e.g. a roll in the paper machine orprinting unit as described later. For the shim matrix a desireddiffractive structure is first originated with an electron beam, a laserbeam, an X-ray beam, an ion beam, or other lithographic method to asuitable substrate coated with a proper resist. Thus a microscopicsurface relief profile is formed in the resist layer. Thereafter thesaid surface is transformed into a negative surface profile in nickel byelectroplating. The result is used to generate second and thirdgeneration shims for mass production. The process of manufacturing shimsis disclosed in detail in “Diffractive Optics”. Third generation shimsare then used in producing package material integrated with the desireddiffractive structures.

The method of embossing diffractive structures in security material isapplicable to various kinds of paper, board, or package material gradessuitable for printing and packaging. Examples of these are common paper(e.g. newsprint, SC paper, coated mechanical paper, uncoated fine paper,coated fine paper), paperboard (e.g. cartonboards, containerboards,special boards), specialty papers (e.g. cable paper, capacitor tissue,conductive paper, decor paper, photographic paper, building papers, sackkraft, flexible packaging, label paper). See “Paper and Board Grades”,part 18 in Papermaking Science and Technology series, ISBN952-5216-18-7, for detailed information of these grades.

FIG. 1 shows an example of a diffractive security structure divided intodifferent security level elements. In this example the diffractivesecurity structure contains areas for various security inspectionlevels. In area A there is a figure that can be identified with bare eyei.e. with first line inspection. Area A comprises two security objectsA1, A2. Object A1 is a simple wave pattern embossed in the paper and itcan be seen by bare eye. Object A2 contains text seen by bare eye at acertain view angle when illuminated suitably. Text in object A2 may alsocontain micro or nano structure information readable only with a secondor third level inspection tools.

In area B there is information that can be read with a second-lineinspection tool, such as a laser pointer. Area B comprises micro or nanodimensional security structures embossed in the material. A laserpointer LP is used for directing a laser beam to point x in area B.Laser beam light diffracts from the security structure in point x andreveals a security structure B1.

Area C comprises micro or nano structures, which are only readable bythird level inspection, tools i.e. state-of-the-art equipment inresearch laboratories. An example of a security object C1 revealed bysuch an inspection tool is shown. Object C1 is a micro scale bar code,which identifies the security, marked object. Alternatively, diffractivestructures containing second and third line inspection levels can behidden in various forms within the area covered by the area of the firstline inspection level structures.

In the method according to the invention for producing security paper orboard or security packages diffractive structures are embossed to thepackage paper or cardboard as described above. In another embodiment ofthe present invention diffractive structures are included in the paperor board product or in the security package material as small piecescontaining diffractive structures. In this method diffractive structuresare embossed in thin sheets of a suitable material, such as aluminium orplastic foil. By grinding, cutting, crushing, or chopping the embossedsheet to small pieces, chopped material with pieces containingdiffractive structures is produced and this material can be mixed to araw material used in paper making or printing process. The choppedmaterial can be mixed for instance into ink, size, paste, resin, orfurnish.

When using furnish mixed with pieces containing diffractive structures,conventional paper and board making machinery can be applied. Using thisapproach in the paper making process, the produced paper or cardboardgets a glittering appearance, which is typical for diffracting surfaces.Similarly well known sizing and coating methods can be used when mixingpieces containing diffractive structures into size or paste. Also,chopped material containing diffractive structures can be added to inkwhich is then useable in any conventional printing system.

Suitable dimensions for chopped material with pieces containingdiffractive structures is of the order of 1 to 10 μm in ink, size, pasteand resin and up to 1 mm in furnish. Information contained in thediffractive elements can be read from security paper or board or packageaccording to the invention using a special reading device. When usingink containing diffractive structures in printing of the securitypackages, the text or pattern printed with diffractive ink containsinformation of the diffractive elements and also this information isreadable with special reading equipment.

The method of embossing or printing the diffractive structures directlyon paper can be carried out e.g. in the following parts of thepapermaking or package manufacturing process:

-   -   on- or off machine calender unit    -   drying unit marketed by Metso Paper, Inc. by the name Condebelt®    -   impulse drying unit    -   flexographic, gravure, offset, or other commercially available        printing systems    -   extrusion coating lines

The method of adding chopped material containing diffractive structuresis applicable in

the following parts of the papermaking or package manufacturing process:

-   -   stock preparation unit    -   sizing unit    -   coating unit    -   flexographic, gravure, offset, or other commercially available        printing systems    -   extrusion coating lines    -   flexible package material lines

FIG. 2 shows a side view of a modern paper or board machine. As shown inFIG. 2, stock is fed from a headbox 100 to a wire section 200 followedby a press section 300. The web W is passed from the press section 300to a dryer section 400 followed by a soft-calendering unit 500. Thefilm-sizing unit 600 is used for treating the web. Surface-sizing,pigmenting, or coating is performed at this stage typically on bothsides of the web at the same time, but the surfaces of the web can alsobe treated separately in successive units. After that, the paper web isdried by using infrared dryers and airborne web-dryers and a shortcylinder group, which follows them.

The web W is coated in coating stations 700, 800 which coat the web W onboth sides. After that, the web W is calendered in a multi-nip calender900, in which the linear load in each nip can be advantageouslyregulated separately. Finally, the web W is passed to a reel-up 1000 inwhich the web is wound into reels.

FIG. 3 shows an example of applying the method of embossing diffractivestructures to paper in a calender. In the calender an extendedcalendering nip N is formed between an upper roll 550 and a shoe roll551. The shoe roll 551 comprises a press shoe 524 supported by astationary beam 525 as well as a calendering belt 520 passed around thepress shoe 524 and the beam 525 and formed as an endless loop. By meansof the press shoe 524, the necessary load is produced in the nip N.According to the invention the upper roll 550 is coated with thediffractive structure shims and the diffractive structures aretransferred to the paper or cardboard web W passing the nip N. Inanother embodiment the calendering belt 520 is coated with diffractivestructure shims. Although a shoe calender has been described above thepresent invention can as well be applied into the prior art hard rollcalenders, soft calenders and supercalenders either on- or off-machine.

FIG. 4 shows a side view of a Condebelt drying system. The Condebeltdrying system is known, e.g., from patent publications FI-54514,FI-61537, and FI-101237. The Condebelt drying system is typically usedin cardboard machines. In the Condebelt drying system the web W carriedon a fine-structured wire 43 and a coarse wire 44 is fed through adrying unit 48, 49 between two smooth steel belts 41, 42. The uppersteel belt 41 contacting the web W is heated while the lower steel belt42 is cooled. Subject to high pressure and temperature difference themoisture in the web W evaporates and the generated vapor traverses thewires 43, 44 to condense on the cooler steel belt or the lower belt 42.The condensed water is taken out from the drying zone. This way driedweb has very advantageous strength characteristics combined with absenceof CD shrinkage. A smooth surface is obtained on one side of the web.The method according to the invention of embossing the diffractivestructures directly on paper or cardboard is applicable in the Condebeltdrying system by providing the heated metal belt wire with thediffractive structure shims.

In an impulse drying process, the web carried on the felt is fed througha pressing nip. The roll contacting the web is heated to temperatureswell above 100° C. In this known process, a very smooth web surface canbe obtained. According to one embodiment of the invention, the heatedroll is provided with the diffractive structure shims to transfer thediffractive marking directly onto the web surface. The impulse dryingprocess is disclosed e.g. in U.S. Pat. No. 4,324,613.

FIG. 5 is a schematic illustration of an example of asurface-sizing/pigmenting unit 600, which is used for sizing and coatingpaper. Surface-sizing/pigmenting systems are disclosed e.g. in FI-93885and FI-81734. The surface-sizing/pigmenting unit 600 comprises rolls 602and 603 of the size press, so that the first roll 602 and the secondroll 603 form a nip N with one another, through which nip the paper orboard web W is passed. In the surface-sizing/pigmenting unit 600, afirst size film F₁ is metered onto the face of the first roll by meansof a first coating device 610 and, in a corresponding way, a second sizefilm F₂ is metered onto the face 605 of the second roll by means of asecond coating device 620. In the roll nip N, the size films F₁ and F₂are transferred to the paper or board web W running through the nip. Thecoated web is denoted with the reference W′. The size films F₁ and F₂are spread onto the faces 604 and 605 of the size press rolls 602, 603using bar coaters, which are equal to one another in this example of asurface-sizing/pigmenting unit 600. In the coating devices 610, 620 thecoating agent is introduced into a pressurized coating-agent chamber616, 626 placed before the coating bar 611, 621. The coating bar 611,621 is fitted in a cradle 612, 622 supporting the coating bar 611, 621over its entire length and is rotated in directions opposite to thedirections of rotation of the rolls 602, 603. According to the inventionchopped material containing diffractive structures is added to size orpaste which is then transferred to the web in thesurface-sizing/pigmenting unit 600.

Extrusion is a process that transfers thermoplastics from a solid to amelted state and compresses them against a substrate using the pressurein a die. FIG. 6 shows an example of an extrusion coating line 1200. Aweb (paper, aluminium or film) W is unwound from a main unwinder 1210.The pre-treatment unit 1220 is used for pre-treating the web W in a waydepending on the material e.g. in order to increase the adhesion. In theextrusion coating unit 1230 a melted resin (LDPE, PP, or other) isextruded on the web W with the extruder 1231. The resin is melted in theextruder 1231 and through a flat die it is extruded on the web andimmediately cooled. The extrusion coating unit 1230 comprises a chillroll 1232 with chromium plated surface, a pressure roller 1233 with arubber surface, and a back-up roller 1234 with chromium plated surface.

In the nip between the pressure roller 1233 and the chill roll 1232 theextruded resin comes in contact with the web. The purpose of the chillroll 1232 is to reduce the temperature of the resin (normally extrudedat temperature ranging from 250° C. to 300° C.) to a value below themelting point in order to prevent the sticking on the chill roll surface1232.

As an alternative, it is possible to laminate two different webs in theextrusion coating unit 1230 using the resin as adhesive. In this casethe second web is coming from the secondary unwinder 1240. It ispossible to use more than one extruder if the product structure requiresdifferent layers. In this case the resins extruded from the extrudersare collected to the die through a feedblock. The purpose of thefeedblock is to collect the materials from the extruders maintaining thedifferent layers. The coated or laminated material obtained with thisprocess is rewound on the rewinder 1290. A thickness gauge 1250 isnormally placed before the rewinder 1290 to measure thickness variationof the final product to be rewound. An automatic control system can beused to manage the extrusion die in order to control the thickness ofthe extruded material.

The method according to the invention is applicable in an extrusion linepreferably in the nip between the pressure roller 1233 and the chillroll 1232. Either of the pressure roller 1233 or the chill roll 1232 isprovided with diffractive structure shims according to the invention.Alternatively, chopped material containing diffractive structures ismixed with the extrusion coating resin.

The method according to the invention is also applicable in the printingprocess of the security paper, board, or package. The printing processcan be carried out in flexographic, gravure, offset, or othercommercially available printing systems. A printing machine isoptionally provided with an embossing unit, which is preferably placedin the printing line after the last printing unit. According to thepresent invention said embossing unit is provided with the diffractivestructure shims to transfer the diffractive marking directly onto theweb surface in the printing line. In another embodiment of the presentinvention chopped material containing diffractive structures is added toink and then transferred to the printed material.

Alternatively, the method of embossing diffractive structures directlyon paper or board or package material according to the invention isapplicable to sheet material also. Sheets of paper, board, or packagematerial can be embossed by stamping with a stamping device. A stampingdevice can be installed e.g. in connection with a sheet cutter inpaper/board machine, printing machine, or such.

Laser pointers are preferable tools for inspecting the authenticity ofthe security paper or board products or security packages according tothe invention. Laser pointers are relatively inexpensive and easy tocarry along so they are available to the public. When pointing asecurity marking according to the invention with a laser beam, specialeffects not seen with the naked eye are revealed. These can be, e.g., acompany or brand logo appearing at or coming out from the securitymarking.

The method according to the invention can be fully integrated to theexisting paper and cardboard machines and coating and printing lines. Noauxiliary systems need to be built.

In addition to using the method according to the invention for producingsecurity marked material for authentication purposes, the same method isapplicable for decorative use.

In the following, the patent claims will be given and various details ofthe invention may show variation within the scope of the inventive ideadefined in the patent claims and differ from the details disclosed abovefor the sake of example only.

1. A method for producing a security paper or board product, saidsecurity product comprising a paper or board security materialfurthermore comprising optical diffractive structures carried by saidsecurity material and containing microstructures or nanostructurescomprising at least a section that is detectable only by second or thirdline inspection tools, wherein the method comprises a step ofintegrating said diffractive structures into said security material in aprinting process of said security material and using a forming surfacecontaining a diffractive shim structure, the method being characterizedin that, in the step of integrating said diffractive structures intosaid security material a security material web is passed through a nipformed between said forming surface and a backing surface, therebyembossing said diffractive structures into said security material webwithout remoisturing the security material web.
 2. The method of claim 1wherein the security material comprises paper or board or flexiblepackaging material having one or more layers of paper, plastic and/ormetal.
 3. The method of claim 1 wherein said diffractive structures areembossed into said security material in a printing unit.
 4. The methodof claim 1 wherein the security material is paper, board, cardboard,corrugated board, printed paper, or printed cardboard.
 5. The method ofclaim 1 wherein the security material is extrusion coated or laminatedmaterial.
 6. The method of claim 1 wherein the diffractive structurescomprise a first section only detectable by said second or third lineinspection tools and at least a second section detectable at a differentinspection level than said first section.